1. Field of the Invention
The present invention relates to an audio and/or video data recording and reproduction apparatus for recording video data of the digital format and reproducing the recorded audio and/or video data.
2. Description of the Related Art
For example, in a television broadcasting station, a video to be telecast in a news program etc. is usually produced by recording and individually managing the video (stock video) and audio serving as the basis of the video to be telecast by a TV camera etc. including a video tape recorder (VTR) on video tapes and having an editor use a VTR in the editing room according to need to reproduce one or more of the audio and/or video data (AV data) recorded on the video tapes and combining the reproduced stock videos to record the video to be actually broadcast on another tape.
However, when the stock videos are managed in the state recorded on video tapes, the work efficiency in selecting the necessary videos from among the large number of stock videos becomes poor. Further, there also exists a need to convey the tapes on which the stock videos are recorded from the storage place to the editing room. Further, it is difficult for a number of editors to use the same stock videos. Such a problem is particularly notable when a large number of stock videos are used for the production of one news video.
Further, the news video produced on the tape is generally carried to and load by hand into a VTR for transmitting the program or a cart machine containing the VTR for transmitting the program. However, since it is necessary to perform the operations such as management of the news videos or changing the order of transmission at the stage of transmitting the program by hand, the efficiency is poor and mistakes can occur due to human error, so the system lacks reliability.
In order to solve such a problem, use is made of a so-called server system as used in a computing system for enabling centralized management and use of the stock videos or the videos for broadcast and therefore shared use of stock videos.
FIG. 1 is a view of an example of the configuration of a example of a server system 8 for audio and/or video data.
As shown in FIG. 1, the server system 8 is basically configured by the basic component elements of the computer, that is, a CPU 401, ROM 402, RAM 403, high speed bus 404, device interfaces 405.sub.m, data recording and reproduction apparatus 406.sub.m connected via the same, input/output interfaces 407.sub.n, audio and/or video data compressing means 408.sub.n connected via the same, and audio and/or video data expanding means 409.sub.n corresponding to the audio and/or video data compressing means 408.sub.n.
Further, where the server system 8 is realized on a computer different from the host application system, a LAN use interface 411 connecting a LAN 410 and the server system 8 is provided.
When the server system 8 records the audio and/or video data, the audio and/or video data compressing means 408.sub.n compress the input audio and/or video data S40.sub.n to generate the compressed audio and/or video data S41.sub.n and transfer the same via the input/output interfaces 407.sub.n to the high speed bus 404.
The compressed audio and/or video data transferred to the high speed bus 404 are usually temporarily stored (buffered) in the RAM 403 for the data flow rate control etc. and then transferred to the bus 404 again and appropriately recorded in the data recording and reproduction apparatuses 406.sub.m via the device interfaces 405.sub.m.
Further, when the server system 8 reproduces the audio and/or video data, the compressed audio and/or video data recorded in the data recording and reproduction apparatuses 406.sub.n are reproduced and then transferred via the device interfaces 405.sub.m to the high speed bus 404.
The compressed audio and/or video data transferred to the high speed bus 404 are buffered in the RAM 403 for the data flow rate control etc. in the same way as that at the recording, transferred again to the high speed bus 404, pass through the input/output interfaces 407.sub.n, and become the input data S42.sub.n to the audio and/or video data expanding means 409.sub.n.
The audio and/or video data expanding means 409.sub.n decode the video signals S43.sub.n from the input data S42.sub.n and output the same from the system.
When the server system 8 records and reproduces the audio and/or video data, the operations of all of the input/output interfaces 407.sub.n, the high speed bus 404, and the device interfaces 405.sub.m are controlled by the CPU 401 based on the commands transferred from the application system via the LAN 410, LAN use interface 411, high speed bus 404, and RAM 403.
Note that, where the operation commands are supplied from not the application system, but from the input/output side of the video signal, control lines S44.sub.n connected to the input/output interfaces 407.sub.n as indicated by the broken lines in FIG. 1 become necessary. In this case, the commands supplied from the control lines S44.sub.n are communicated to the CPU 401 via the input/output interfaces 407.sub.n, the high speed bus 404, and the RAM 403, and the CPU 401 controls the operation of the input/output interfaces 407.sub.n, high speed bus 404, and the device interfaces 405.sub.m based on the commands supplied from the control lines S44.sub.n.
FIG. 2 is a view of the configuration of an editing system 9 using the server system 8 shown in FIG. 1.
When audio and/or video data are edited by using the server system 8, as shown in for example FIG. 2, use is made of an editing system 9 comprised of editing apparatuses 90.sub.1 and 90.sub.2, connected to a server system 8, each of which having two audio and/or video data input terminals and one audio and/or video output terminal (AV) and a control signal terminal (C) corresponding to each of these audio and/or video signal input/output terminals and performing cutting to connect a plurality of audio and/or video data or addition of special effects to the audio and/or video data. The editor edits the audio and/or video data supplied from the server system 8 by using the editing apparatuses 90.sub.1 and 90.sub.2 and records the result in the server system 8 again.
However, the server system 8 shown in FIG. 1 is not always suitable for recording and reproducing the high quality audio and/or video data of a television broadcasting station. The reason for this will be explained below.
First, if the server system 8 were to handle the high quality audio and/or video data of a level as used in a television broadcasting station, the data transfer capability of its bus would be insufficient and the system size or an expansion property of the system would be limited.
That is, the data rate of the current digital format of the television audio and/or video data is 100 Mbps or more. Also, the coded audio and/or video data obtained by high efficient coding of this audio and/or video data has a data rate of about 30 Mbps (4 MBps), as disclosed in for example the CCIR recommendation 723, taking the deterioration due to the editing into account.
For example, if trying to allow eight editors to simultaneously perform editing (so-called AB roll editing) using two stock videos of 30 Mbps (4 MBps) in the server system 8, when taking the necessity of buffering the audio and/or video data as mentioned above into account, as much as 48 [=3 (due to the necessity of simultaneously reproducing two stock videos and recording one video after editing).times.2 (reciprocation for buffering).times.8 (number of editors)] series of coded audio and/or video data would be simultaneously transferred on the high speed bus 404. Accordingly, an effective data transfer rate of 192 Mbps a the lowest would be required for just the transfer of the coded audio and/or video data to the high speed bus 404.
Further, when transferring the audio and/or video data to the input/output interfaces 407.sub.n, there is a limitation inherent in the server system 8 in a television broadcasting station that no instantaneous disconnection may occur. Therefore, there also arises a problem of the processing capability of the CPU 401 controlling the high speed bus 404 and the RAM 403. In addition, the physical transfer speed of the bus in a high performance computer is usually about 100 Mbps. According to the configuration of the server system 8 shown in FIG. 1, realization of editing in which as many as about eight editors can share the use of the stock video is not always technically easy.
Further, when realizing a server system useable in a television broadcasting station, the server system must be brought into slave synchronization with a synchronization signal or time stamp supplied from the outside.
Usually, the transmission and reception of audio and/or video data between the broadcasting equipment in a television broadcasting station are carried out in strict synchronization with a reference synchronization signal or time code for the audio and/or video data.
Accordingly, to connect the already existing broadcasting apparatuses with a server system, it is necessary to input and output (input/output) the audio and/or video data of the server system in synchronization with the reference synchronization signal or the like. However, in a server system 8, which performs the transfer of audio and/or video data by using a basically asynchronously operating computer, it is not always easy to input/output the audio and/or video data in synchronization with a reference synchronization signal or time code.
That is, in the server system 8 having the configuration shown in FIG. 1, when the transfer and exchange (routing) of the audio and/or video data are carried out by using the asynchronous high speed bus 404 and RAM 403, after the audio and/or video data to be originally transmitted in synchronization with the reference synchronization signal etc. have passed through the asynchronous transfer system inside the server system 8, synchronous/asynchronous conversion processing for bringing the same into synchronization with the external reference synchronization signal again becomes necessary. Therefore, the size of the apparatus becomes larger and also the manufacturing cost rises.
Further, in the editing system 9 shown in FIG. 2, each of the editing apparatuses 90.sub.1 and 90.sub.2 must be provided with all of the data processing means for the editing. Provision, for example, of an expensive data processing means which is rarely used in each of the editing apparatuses 90.sub.1 and 90.sub.2 raises the cost of the editing apparatuses 90.sub.1 and 90.sub.2.
The server system 8 and the editing system 9 shown in FIG. 1 suffer from the problems as mentioned above. It is necessary to find measures to solve these problems.